Host C also receives the frame from host A to host B, but because the destination MAC address of that frame is host B, host C drops that frame.Ĭlick the Step 3 button in the figure to see the next step. The switch then learns that the MAC address for host B is located on port 2 and writes that information into the MAC address table. Host B receives the frame and sends a reply to host A.
If the switch cannot find the destination MAC in the MAC address table, the switch then copies the frame and broadcasts it out every switch port.Ĭlick the Step 2 button in the figure to see the next step. The switch receives the frames and looks up the destination MAC address in its MAC address table. In the figure, host A sends traffic to host B. To understand the mechanism of a MAC address table overflow attack, recall the basic operation of a switch.Ĭlick the Step 1 button in the figure to see how MAC address table overflow attack begins. MAC address table overflow attacks are sometimes referred to as MAC flooding attacks. If the MAC address does not exist, the switch acts like a hub and forwards the frame out every port on the switch. If an entry exists for the MAC address, the switch forwards the frame to the MAC address port designated in the MAC address table. As frames arrive on switch ports, the source MAC addresses are learned and recorded in the MAC address table. All Catalyst switch models use a MAC address table for Layer 2 switching. When a Layer 2 switch receives a frame, the switch looks in the MAC address table for the destination MAC address. Recall that the MAC address table in a switch contains the MAC addresses available on a given physical port of a switch and the associated VLAN parameters for each. If you find network security of interest, you should explore the course CCNA Exploration: Accessing the WAN. The details of how some of these common attacks work are beyond the scope of the course. This topic provides introductory level information about security attacks. In this topic, you will learn about a few common security attacks and how dangerous they are. Unfortunately, basic switch security does not stop malicious attacks from occurring.